KEITH BARKER CCIE No. 6783 KEVIN WALLACE CCIE No. 7945 MICHAEL D. TAYLOR Learn, prepare, and practice for exam success N10-006 Cert Guide Save 10% on Exam Voucher See Inside Includes a free copy of the CompTIA Network+ N10-006 Hands-on Lab Simulator!
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Deluxe Edition
Companion DVD
KEITH BARKER CCIE No. 6783KEVIN WALLACE CCIE No. 7945MICHAEL D. TAYLOR
Learn, prepare, and practice for exam success
N10-006
Cert Guide
Cert G
uide
Cert Guide CompTIA Network+ N10-006 Cert Guide, Deluxe Edition contains proven study features that enable you to succeed on the exam the first time. Best-selling authors and expert instructors Keith Barker and Kevin Wallace share preparation hints and test-taking tips, helping you identify areas of weakness and improve both your conceptual knowledge and hands-on skills, essential for successful completion of the performance-based testing items on the exam. This complete, CompTIA-approved study package includes the following:
BARKERWALLACETAYLOR
N10-006
N10-006
Pearson IT Certification Practice Test Minimum System Requirements:
Windows Vista (SP2), Windows 7, or Windows 8.1 (desktop UI only); Microsoft .NET Framework 4.5 Client; Pentium-class 1 GHz processor (or equivalent); 512 MB RAM, 650 MB disk space, plus 50 MB for each downloaded practice exam; access to the Internet to register and download exam databases
The DVD contains more than 400 prac-tice questions, 40 performance-based question exercises, glossary flash
cards, an exam essentials review tool, memory table exercises and answer keys, a study plan-ner tool, more than 60 minutes of video, and the Network+ Simulator.
Includes a free copy of the CompTIA Network+ N10-006 Hands-on Lab Simulator!
This approved study guide helps you master topics on the CompTIA Network+ N10-006 exam, including the following:
u Computer network fundamentalsu The OSI model and TCP/IP stacku Media types, infrastructure
components, and network devicesu Ethernet technologyu IPv4 and IPv6 addressesu Routing IP traffic with dynamic
routing protocolsu DNAT, SNAT, and PATu Multicast routingu Wide Area Networks (WANs)u Wireless LANsu Network optimization and QoSu Windows and UNIX command-line
tools for network administration and troubleshooting
u Network securityu Troubleshooting common Layer 2,
Layer 3, and wireless networking issues
u A test-preparation routine proven to help you pass the exams approved by CompTIA
u Clearly defined chapter learning objectives covering all N10-006 exam topics
u Chapter-ending review questions and exam preparation exercises, which help you drill on key concepts you must know thoroughly
u The powerful Pearson IT Certification Practice Test software, complete with hundreds of well reviewed, exam-realistic questions, customization options, and detailed performance reports
u 40 performance-based practice question exercises to help you prepare for the hands-on exam questions
u More than 60 minutes of video mentoring from the author
u A final preparation chapter, which guides you through tools and resources to help you craft your review and test-taking strategies
u An Exam Essentials appendix that quickly recaps all major chapter topics for easy reference, both in print and interactive digital format
u A key terms Glossary in both print and on the DVD, which acts as an interactive flash-card application
u Study plan suggestions and templates to help you organize and optimize your study time
u A 10% exam discount voucher (a $27 value!)
This Deluxe Edition also includes two special features:
u A free copy of the CompTIA Network+ N10-006 Authorized Cert Guide Premium Edition eBook and Practice Test. This package provides you access to three eBook files (PDF, EPUB, and Mobi/Kindle format), more than 400 exam-realistic practice test questions, and links from all the questions to the specific sections in the PDF eBook file for detailed explanations and review.
u A free copy of the CompTIA Network+ N10-006 Hands-on Lab Simulator, including 63 hands-on practice labs covering real-world network configuration scenarios in Windows GUI and Cisco router and switch CLI environments, hardware activities, network design exercises, and technology mapping tasks.
KEITH BARKER, CCIE NO. 6783, has been working in the IT industry since 1985. He currently enjoys creating effective and entertaining video training for CBT Nuggets.
KEVIN WALLACE, CCIEX2 (COLLABORATION AND R/S) NO. 7945, has been a network design specialist, an instructor of networking courses, and a network manager. He currently produces video courses and books for Pearson (http://kwtrain.com/books).
Lab Simulator AuthorMICHAEL D. TAYLOR is the computer sciences department head for a career college in the eastern US, where he has taught for the last 10 years.
All terms mentioned in this book that are known to be trademarks or ser-vice marks have been appropriately capitalized. Pearson cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark.Windows is a registered trademark of Microsoft Corporation.
Warning and Disclaimer
Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information provided is on an “as is” basis. The author and the publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book or from the use of the DVD or programs accompanying it.
Special Sales
For information about buying this title in bulk quantities, or for special sales opportunities (which may include electronic versions; custom cover designs; and content particular to your business, training goals, marketing focus, or branding interests), please contact our corporate sales department at [email protected] or (800) 382-3419.For government sales inquiries, please contact [email protected] questions about sales outside the U.S., please contact [email protected].
Associate Publisher
Dave Dusthimer
Executive Editor
Brett Bartow
Senior Development
Editor
Christopher Cleveland
Managing Editor
Sandra Schroeder
Project Editor
Seth Kerney
Copy Editor
Keith Cline
Indexer
Tim Wright
Proofreader
Gill Editorial Services
Technical Editors
Michelle Plumb
Anthony Sequeria
Publishing Coordinator
Vanessa Evans
Multimedia Developer
Lisa Matthews
Book Designer
Mark Shirar
Composition
Trina Wurst
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Contents at a Glance
Introduction xxv
CHAPTER 1 Computer Network Fundamentals 2
CHAPTER 2 The OSI Reference Model 28
CHAPTER 3 Network Components 60
CHAPTER 4 Ethernet Technology 112
CHAPTER 5 IPv4 and IPv6 Addresses 148
CHAPTER 6 Routing IP Packets 198
CHAPTER 7 Wide-Area Networks 230
CHAPTER 8 Wireless LANs 266
CHAPTER 9 Network Optimization 296
CHAPTER 10 Command-Line Tools 326
CHAPTER 11 Network Management 366
CHAPTER 12 Network Security 396
CHAPTER 13 Network Troubleshooting 450
CHAPTER 14 Final Preparation 476
APPENDIX A Answers to Review Questions 486
APPENDIX B Network+ N10-006 Exam Updates 490
APPENDIX C Exam Essentials 494
Glossary 506
Index 533
ON THE DVD:
APPENDIX D Memory Tables
APPENDIX E Memory Table Answer Key
APPENDIX F Study Planner
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iv CompTIA Network+ N10-006 Cert Guide, Deluxe Edition
Table of Contents
Introduction xxv
Chapter 1 Computer Network Fundamentals 2
Foundation Topics 4
Defining a Network 4
The Purpose of Networks 4
Overview of Network Components 5
Networks Defined by Geography 7
LAN 7
WAN 8
Other Categories of Networks 8
CAN 8
MAN 8
PAN 9
Networks Defined by Topology 9
Physical Versus Logical Topology 9
Bus Topology 11
Ring Topology 13
Star Topology 14
Hub-and-Spoke Topology 15
Full-Mesh Topology 17
Partial-Mesh Topology 18
Networks Defined by Resource Location 19
Client/Server Networks 19
Peer-to-Peer Networks 21
Real-World Case Study 22
Summary 23
Exam Preparation Tasks 23
Review Questions 25
Chapter 2 The OSI Reference Model 28
Foundation Topics 30
The Purpose of Reference Models 30
The OSI Model 31
Layer 1: The Physical Layer 33
Layer 2: The Data Link Layer 37
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Contents v
Media Access Control 37
Logical Link Control 38
Layer 3: The Network Layer 40
Layer 4: The Transport Layer 42
Layer 5: The Session Layer 44
Layer 6: The Presentation Layer 46
Layer 7: The Application Layer 47
The TCP/IP Stack 48
Layers of the TCP/IP Stack 48
Common Application Protocols in the TCP/IP Stack 51
Real-World Case Study 55
Summary 56
Exam Preparation Tasks 56
Review Questions 58
Chapter 3 Network Components 60
Foundation Topics 62
Media 62
Coaxial Cable 62
Twisted-Pair Cable 64
Shielded Twisted Pair 64
Unshielded Twisted Pair 65
Plenum Versus Nonplenum Cable 68
Fiber-Optic Cable 69
Multimode Fiber 69
Single-Mode Fiber 71
Fiber Connector Polishing Styles 73
Media Converters 74
Cable Distribution 74
Wireless Technologies 76
Network Infrastructure Devices 77
Hubs 77
Bridges 79
Switches 80
Multilayer Switches 87
Routers 88
Infrastructure Device Summary 89
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Specialized Network Devices 90
VPN Concentrators 90
Firewalls 91
DNS Servers 92
DHCP Servers 94
Proxy Servers 96
Content Engines 97
Content Switches 98
Virtual Network Devices 99
Virtual Servers 99
Virtual Routers and Firewalls 100
Virtual Switches 101
Virtual Desktops 102
Other Virtualization Solutions 102
Cloud Computing 103
Software-Defined Networking 104
Voice over IP Protocols and Components 104
Real-World Case Study 105
Summary 106
Exam Preparation Tasks 107
Review Questions 109
Chapter 4 Ethernet Technology 112
Foundation Topics 114
Principles of Ethernet 114
Ethernet Origins 114
Carrier Sense Multiple Access Collision Detect 116
Distance and Speed Limitations 120
Ethernet Switch Features 122
Virtual LANs 122
Switch Configuration for an Access Port 124
Trunks 125
Switch Configuration for a Trunk Port 127
Spanning Tree Protocol 127
Corruption of a Switch’s MAC Address Table 128
Broadcast Storms 129
STP Operation 130
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Contents vii
Link Aggregation 133
LACP Configuration 134
Power over Ethernet 135
Port Monitoring 136
Port Mirroring Configuration 138
User Authentication 138
Management Access and Authentication 140
First-Hop Redundancy 141
Other Switch Features 142
Real-World Case Study 143
Summary 144
Exam Preparation Tasks 144
Review Questions 146
Chapter 5 IPv4 and IPv6 Addresses 148
Foundation Topics 150
Binary Numbering 150
Principles of Binary Numbering 150
Converting a Binary Number to a Decimal Number 151
Converting a Decimal Number to a Binary Number 151
Binary Numbering Practice 153
Binary Conversion Exercise 1 153
Binary Conversion Exercise 1: Solution 154
Binary Conversion Exercise 2 154
Binary Conversion Exercise 2: Solution 154
Binary Conversion Exercise 3 154
Binary Conversion Exercise 3: Solution 155
Binary Conversion Exercise 4 155
Binary Conversion Exercise 4: Solution 156
IPv4 Addressing 157
IPv4 Address Structure 157
Classes of Addresses 159
Types of Addresses 161
Unicast 161
Broadcast 161
Multicast 162
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Case Study: SOHO Network Design 313Case Study Scenario 313Suggested Solution 315IP Addressing 315Layer 1 Media 317Layer 2 Devices 317Layer 3 Devices 318Wireless Design 318Environmental Factors 319Cost Savings Versus Performance 320Topology 320
Real-World Case Study 320Summary 321Exam Preparation Tasks 322Review Questions 323
Chapter 10 Command-Line Tools 326
Foundation Topics 328
Windows Commands 328
arp 328
ipconfig 330
nbtstat 333
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Contents xiii
netstat 336
nslookup 338
ping 340
ping with IPv6 342
route 342
tracert 346
tracert with IPv6 347
PathPing 348
UNIX Commands 348
arp 349
dig and nslookup 352
host 353
ifconfig 353
traceroute 354
traceroute for IPv6 355
netstat 355
ping 357
Real-World Case Study 359
Summary 360
Exam Preparation Tasks 360
Review Questions 362
Chapter 11 Network Management 366
Foundation Topics 368
Maintenance Tools 368
Bit-Error Rate Tester 368
Butt Set 369
Cable Certifier 369
Cable Tester 370
Connectivity Software 370
Crimper 370
Electrostatic Discharge Wrist Strap 371
Environmental Monitor 372
Loopback Plug 373
Multimeter 373
Protocol Analyzer 374
WiFi Analyzer 375
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xiv CompTIA Network+ N10-006 Cert Guide, Deluxe Edition
Looking-Glass Sites 375
Speed Test Sites 376
Punch-Down Tool 376
Throughput Tester 376
Time Domain Reflectometer/Optical Time Domain Reflectometer 377
Toner Probe 378
Configuration Management 378
Monitoring Resources and Reports 381
SNMP 381
Syslog 385
Logs 387
Application Logs 388
Security Logs 388
System Logs 389
Real-World Case Study 389
Summary 390
Exam Preparation Tasks 391
Review Questions 392
Chapter 12 Network Security 396
Foundation Topics 398
Security Fundamentals 398
Network Security Goals 398
Confidentiality 398
Symmetric Encryption 399
Asymmetric Encryption 400
Integrity 402
Availability 403
Categories of Network Attacks 403
Confidentiality Attacks 403
Integrity Attacks 407
Availability Attacks 409
Denial of Service 410
Distributed Denial of Service 410
TCP SYN Flood 410
Buffer Overflow 411
ICMP Attacks 411
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Contents xv
Electrical Disturbances 412
Attacks on a System’s Physical Environment 413
Physical Controls 414
Defending Against Attacks 414
User Training 414
Patching 415
Security Policies 416
Governing Policy 417
Technical Policies 418
End-User Policies 418
More Detailed Documents 418
Incident Response 419
Vulnerability Scanners 420
Nessus 420
Nmap 421
Honey Pots and Honey Nets 422
Access Control Lists 423
Remote-Access Security 424
Firewalls 426
Firewall Types 426
Firewall Inspection Types 427
Packet-Filtering Firewall 427
Stateful Firewall 428
Firewall Zones 429
Unified Threat Management Firewalls 430
Virtual Private Networks 431
Overview of IPsec with IKEv1 433
IKE Modes and Phases 433
Authentication Header and Encapsulating Security Payload 435
The Five Steps in Setting Up and Tearing Down an IPsec Site-to-Site VPN Using IKEv1 437
Other VPN Technologies 438
Intrusion Detection and Prevention 439
IDS Versus IPS 439
IDS and IPS Device Categories 440
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xvi CompTIA Network+ N10-006 Cert Guide, Deluxe Edition
Detection Methods 440
Signature-Based Detection 440
Policy-Based Detection 441
Anomaly-Based Detection 441
Deploying Network-Based and Host-Based Solutions 442
Real-World Case Study 443
Summary 444
Exam Preparation Tasks 445
Review Questions 447
Chapter 13 Network Troubleshooting 450
Foundation Topics 452
Troubleshooting Basics 452
Troubleshooting Fundamentals 452
Structured Troubleshooting Methodology 454
Physical Layer Troubleshooting 457
Physical Layer Troubleshooting: Scenario 458
Physical Layer Troubleshooting: Solution 459
Data Link Layer Troubleshooting 460
Data Link Layer Troubleshooting: Scenario 461
Data Link Layer Troubleshooting: Solution 461
Network Layer Troubleshooting 462
Layer 3 Data Structures 462
Common Layer 3 Troubleshooting Issues 464
Network Layer Troubleshooting: Scenario 465
Network Layer Troubleshooting: Solution 466
Wireless Troubleshooting 467
Wireless Network Troubleshooting: Scenario 469
Wireless Network Troubleshooting: Solution 469
Specialized Networks 470
Real-World Case Study 470
Summary 471
Exam Preparation Tasks 472
Review Questions 473
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Contents xvii
Chapter 14 Final Preparation 476
Tools for Final Preparation 477
Pearson Cert Practice Test Engine and Questions on the DVD 477
Install the Software from the DVD 478
Activate and Download the Practice Exam 479
Activating Other Exams 480
Premium Edition 480
Video Training on DVD 480
Memory Tables 481
Simulations and Performance-Based Exercises 481
End-of-Chapter Review Tools 481
Suggested Plan for Final Review and Study 481
Strategies for Taking the Exam 483
Summary 484
APPENDIX A Answers to Review Questions 486
APPENDIX B Network+ N10-006 Exam Updates 490
APPENDIX C Exam Essentials 494
Glossary 506
Index 533
ON THE DVD:
APPENDIX D Memory Tables
APPENDIX E Memory Table Answer Key
APPENDIX F Study Planner
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xviii CompTIA Network+ N10-006 Cert Guide, Deluxe Edition
About the Book AuthorsKeith Barker, CCIE No. 6783, has been working in the information technology (IT) industry since 1985. He currently enjoys creating effective and entertaining video training for CBT Nuggets. He has certified with VMware, Cisco, Juniper, HP, Check Point, Palo Alto, (ISC)2, and many others. Keith loves to teach. You can follow Keith online through the following:
Twitter: @KeithBarkerCCIE
Facebook: Keith Barker Networking
YouTube: http://youtube.com/Keith6783
Web page: http://cbtnuggets.com
Kevin Wallace, CCIE No. 7945 (R/S and Collaboration), is a Certified Cisco Sys-tems Instructor (CCSI No. 20061) with multiple Cisco professional and associate-level certifications in the R/S, Collaboration, Security, Design, and Data Center tracks. With networking experience dating back to 1989, Kevin has been a network design specialist for the Walt Disney World Resort, an instructor of Cisco courses for Skillsoft, and a network manager for Eastern Kentucky University.
Currently, Kevin owns and operates Kevin Wallace Training, LLC, where he pri-marily produces video courses and writes books for Cisco Press/Pearson IT Certifi-cation (http://kwtrain.com/books).
Kevin holds a bachelor of science degree in electrical engineering from the Uni-versity of Kentucky, and he lives in central Kentucky with his wife (Vivian) and two daughters (Stacie and Sabrina).
Kevin can be followed on these social media platforms:
Blog: http://kwtrain.com
Twitter: http://twitter.com/kwallaceccie
Facebook: http://facebook.com/kwallaceccie
YouTube: http://youtube.com/kwallaceccie
LinkedIn: http://linkedin.com/in/kwallaceccie
Google+: http://google.com/+KevinWallace
About the Network+ Hands-On Lab Simulator Author:Network+ certified since 2003, Michael Taylor currently serves as computer sci-ences department head for a career college in the eastern United States, where he has taught for more than 10 years. In his role as a technical instructor, he won the Instructor of the Year award from his superiors and Instructor of the Quarter award from his students numerous times. In addition to a bachelor degree in business administration from the University of North Carolina at Chapel Hill, Mr. Taylor holds a master’s degree in industrial technology with a concentration in computer network management from East Carolina University.
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Dedication xix
Dedication
Keith: This book is dedicated to individuals from all backgrounds and experiences who are taking deliberate steps to improve their knowledge, life, and community. May you have measureable success in your journey!
Kevin: My contributions to this book are dedicated to you, the reader. The CompTIA Network+ certifi cation can be your fi rst step in a long and rewarding career in networking. May the concepts in this book fuel your passion for continuous learning.
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xx CompTIA Network+ N10-006 Cert Guide, Deluxe Edition
Acknowledgments
Keith Barker:
All the professionals at Pearson IT Certification have been fantastic to work with, including Brett Bartow and Christopher (Chris) Cleveland. Many thanks to all of Pearson IT.
CBT Nuggets has been very supportive of me in all my endeavors. I am grateful on a daily basis for the amazing opportunity that Dan Charbonneau and the CBT Nuggets team represents for both me and the learners around the globe who enjoy CBT Nuggets videos.
Thanks to longtime friend Kevin Wallace for allowing me to work with him on this latest version of book, and for Anthony and Michelle for their sweet tech edits.
Kevin Wallace:
A huge “thank you” goes out to my good friend Keith Barker for taking the lead on this book. Your insight into these technologies is profound, and your enthusiasm is contagious.
Also, I am grateful to work with the team of professionals at Pearson IT Certifica-tion. You are all a class act.
As always, I’m thankful to God and His many blessings, not the least of which is my family (my wife, Vivian, and daughters, Sabrina and Stacie).
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About the Technical Editors xxi
About the Technical Editors
Michelle Plumb is a full-time Cisco Certified Systems Instructor (CCSI). She has 26-plus years of experience in the field as an IT professional and telecommunications specialist. She maintains a high level of Cisco, Microsoft, and CompTIA certifications, including CCNP Voice, MCSE, CompTIA A+, Network+, Project+, and iNet+. Michelle has been a technical reviewer for numerous books related to the Cisco CCNP Route and Switch, CCNP Voice, and CompTIA course materials. Her main passion is helping others learn these new and exciting technologies. She lives in Phoe-nix, Arizona, with her husband and two dogs.
Anthony Sequeira, CCIE No. 15626, is a seasoned trainer and author on all levels and tracks of Cisco certification. Anthony formally began his career in the IT in-dustry in 1994 with IBM in Tampa, Florida. He quickly formed his own computer consultancy, Computer Solutions, and then discovered his true passion: teaching and writing about Microsoft and Cisco technologies.
Anthony joined Mastering Computers in 1996 and lectured to massive audiences around the world about the latest in computer technologies. Mastering Computers became the revolutionary online training company KnowledgeNet, and Anthony trained there for many years.
Anthony is currently pursuing his second CCIE in the area of security and then his third Cisco Data Center. When he’s not writing for Cisco Press, Anthony is a full-time instructor at CBT Nuggets.
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We Want to Hear from You!As the reader of this book, you are our most important critic and commentator. We value your opinion and want to know what we’re doing right, what we could do bet-ter, what areas you’d like to see us publish in, and any other words of wisdom you’re willing to pass our way.
We welcome your comments. You can email or write to let us know what you did or didn’t like about this book—as well as what we can do to make our books better.
Please note that we cannot help you with technical problems related to the topic of this book.
When you write, please be sure to include this book’s title and author as well as your name, email address, and phone number. I will carefully review your comments and share them with the author and editors who worked on the book.
Mail: Pearson IT CertificationATTN: Reader Feedback800 East 96th StreetIndianapolis, IN 46240 USA
Reader ServicesVisit our website and register this book at http://www.pearsonitcertification.com/title/9780789754738 for convenient access to any updates, downloads, or errata that might be available for this book.
CompTIA Network+The CompTIA Network+ (N10-006) certification exam will test to determine that the successful candidate has the knowledge and skills required to configure, manage and troubleshoot a network that uses Internet Protocol (IP).
It Pays to Get Certified
In a digital world, digital literacy is an essential survival skill. Certification proves that you have the knowledge and skill to solve business problems in nearly any busi-ness environment. Certifications are highly valued credentials that qualify you for jobs, increased compensation, and promotion.
■ The CompTIA Network+ credential: Proves knowledge of networking fea-tures and functions and is the leading vendor-neutral certification for network-ing professionals.
■ Career pathway: CompTIA Network+ is the first step in starting a network-ing career. Hundreds of thousands of individuals worldwide are CompTIA Network+ certified.
■ Mandated/recommended by organizations worldwide: Such as Cisco, HP, Ricoh, the U.S. State Department, and U.S. government contractors such as EDS, General Dynamics, and Northrop Grumman.
How Certification Helps Your Career
CompTIA Career Pathway
CompTIA offers a number of credentials that form a foundation for your career in technology and allow you to pursue specific areas of concentration. Depending on the path you choose to take, CompTIA certifications help you build upon your skills and knowledge, supporting learning throughout your entire career.
Steps to Getting Certified and Staying Certified
Review exam objectives
Review the certification objectives to make sure that you know what is covered in the exam: http://certification.comptia.org/training/testingcenters/examobjectives.aspx.
Practice for the exam
After you have studied for the certification, take a free assessment and sample test to get an idea of what type of questions might be on the exam: http://certification.comptia.org/training/testingcenters/samplequestions.aspx.
Purchase your exam voucher on the CompTIA Marketplace, which is located at http://www.comptiastore.com/.
Take the test! Select a certification exam provider and schedule a time to take your exam. You can find exam providers at http://certification.comptia.org/training/testingcenters.aspx.
Stay certified!Continuing education
CompTIA Network+ certifications are valid for three years from the date of certification. There are a number of ways the certification can be renewed. For more information, go to http://certification.comptia.org/stayCertified.aspx.
Why CompTIA?
■ Global recognition: CompTIA is recognized globally as the leading IT non-profit trade association and has enormous credibility. Plus, CompTIA’s cer-tifications are vendor-neutral and offer proof of foundational knowledge that translates across technologies.
■ Valued by hiring managers: Hiring managers value CompTIA certification because it is vendor- and technology-independent validation of your technical skills.
■ Recommended or required by government and businesses: Many govern-ment organizations and corporations either recommend or require technical staff to be CompTIA certified.
How to Obtain More Information from CompTIA
■ Visit CompTIA online: Visit http://www.comptia.org to learn more about getting CompTIA certified.
IntroductionThe CompTIA Network+ certification is a popular certification for those entering the computer networking field. Although many vendor-specific networking certifi-cations are popular in the industry, the CompTIA Network+ certification is unique in that it is vendor neutral. The CompTIA Network+ certification often acts as a stepping-stone to more specialized and vendor-specific certifications, such as those offered by Cisco Systems.
In CompTIA Network+, the topics are mostly generic in that they can apply to networking equipment regardless of vendor. Although the CompTIA Network+ is vendor neutral, network software and systems are implemented by multiple inde-pendent vendors. In that light, several of the exercises, examples, and simulations in this book include using a vendor’s configuration and technology such as Microsoft Windows operating systems or Cisco Systems routers and switches. More detailed training for a specific vendor’s software and hardware can be found in books and training specific to that vendor.
Goals and MethodsThe goal of this book is to assist you in learning and understanding the technologies covered in the Network+ N10-006 blueprint from CompTIA. This also allows you to demonstrate that knowledge by passing the N10-006 version of the CompTIA Network+ exam.
To aid you in mastering and understanding the Network+ certification objectives, this book uses the following methods:
■ Opening topics list: This defines the topics that are covered in the chapter.
■ Foundation topics: At the heart of a chapter, this section explains the topics from a hands-on and a theory-based standpoint. This includes in-depth de-scriptions, tables, and figures that build your knowledge so that you can pass the N10-006 exam. The chapters are each broken into multiple sections.
■ Key topics: This indicates important figures, tables, and lists of information that you need to know for the exam. They are sprinkled throughout each chapter and are summarized in table format at the end of each chapter.
■ Memory tables: You can find these on the DVD within Appendixes D and E. Use them to help memorize important information.
■ Key terms: Key terms without definitions are listed at the end of each chap-ter. Write down the definition of each term, and check your work against the complete key terms in the Glossary. On the DVD, you will find a flash card application with all the glossary terms separated by chapter, so feel free to use that to study key terms as well.
■ Exercises: This book comes with 40 performance-based practice exercises that are designed to help you prepare for the hands-on portion of the Network+ exam. These exercises are available on the DVD. Make sure you do the exer-cises as you complete each chapter and again when you have completed the book and are doing your final preparation.
■ Hands-on Labs: These include matching, drag and drop, and simulations. These hands-on exercises are an important part of this book. In addition to reading this book, you should go through all the exercises included with the book. These interactive hands-on exercises provide examples, additional infor-mation, and insight about a vendor’s implementation of the technologies. To perform the labs, simply install the CompTIA Network+ N10-006 Hands-on Lab Simulator software from the DVD.
■ Practice Exams: This book comes complete with several full length practice exams available to you in the Pearson IT Certification Practice Test software on the DVD. Be sure to run through the questions in Exam Bank 1 as you complete each chapter in study mode. When you have completed the book, take a full practice test using Exam Banks 2-4 questions in practice exam mode to test your exam readiness.
■ Exam Essentials: This book includes an Exam Essentials appendix that sum-maries the key points from every chapter. This review tool is available in both print and an interactive PDF on the DVD. Review these essential exam facts after each chapter and again when you have completed the book. This makes a great review summary that you can mark up as you review and master each concept.
For current information about the CompTIA Network+ certification exam, visit http://certification.comptia.org/getCertified/certifications/network.aspx.
Who Should Read This Book?Readers will range from people who are attempting to attain a position in the IT field to people who want to keep their skills sharp or perhaps retain their job be-cause of a company policy that mandates they take the new exams.
This book is also for the reader who wants to acquire additional certifications be-yond the Network+ certification (for example, the Cisco Certified Network Associ-ate [CCNA] certification and beyond). The book is designed in such a way to offer easy transition to future certification studies.
Strategies for Exam PreparationThis book comes with a study planner tool on the DVD. This spreadsheet helps you keep track of the activities you need to perform in each chapter and helps you organize your exam preparation tasks. As you read the chapters in this book, jot down notes with key concepts or configurations in the study planner. Each chapter ends with a summary and series of exam preparation tasks to help you reinforce what you learned. These tasks include review exercises like reviewing key topics, completing memory tables, de-fining key terms, answering review questions, performing hands-on labs and exercises, and so on. Make sure you perform these tasks as you complete each chapter to improve your retention of the material and record your progress in the study planner.
The book concludes with a Final Preparation chapter that offers you guidance on your final exam preparation and provides you with some helpful exam advice. Make sure you read over that chapter to help you assess your exam readiness and identify areas where you need to focus your review.
Make sure you complete all the performance-based question exercises and hands-on labs associated with this book. The exercises and labs are organized by chapter, mak-ing it easy to perform them after you complete each section. These exercises will re-inforce what you have learned, offer examples of some popular vendors methods for implementing networking technologies, and provide additional information to assist you in building real-world skills and preparing you for the certification exam.
Download the current exam objectives by submitting a form on the following web page: http://certification.comptia.org/training/testingcenters/examobjectives.aspx.
Use the practice exam, which is included on this book’s DVD. As you work through the practice exam, use the practice test software reporting features to note the areas where you lack confidence and review those concepts. After you review these areas, work through the practice exam a second time and rate your skills. Keep in mind that the more you work through the practice exam, the more familiar the questions become, and the practice exam becomes a less-accurate judge of your skills.
After you work through the practice exam a second time and feel confident with your skills, schedule the real CompTIA Network+ exam (N10-006). The following website provides information about registering for the exam: http://certification.comptia.org/training/testingcenters.aspx.
CompTIA Network+ Exam TopicsTable I-1 lists general exam topics (objectives) and specific topics under each gen-eral topic (subobjectives) for the CompTIA Network+ N10-006 exam. This table lists the primary chapter in which each exam topic is covered. Note that many ob-jectives and subobjectives are interrelated and are addressed in multiple chapters within the book itself.
1.0 Network architecture 1.1 Explain the functions and applications of various network devices1.6 Differentiate between common network topologies1.7 Differentiate between network infrastructure implementations
2 The OSI Reference Model
5.0 Industry standards, practices, and network theory
5.1 Analyze a scenario and determine the corresponding OSI layer5.2 Explain the basics of network theory and concepts5.9 Compare and contrast ports and protocols5.10 Given a scenario, configure and apply the appropriate ports and protocols
3 Network Components
1.0 Network architecture5.0 Industry standards, practices, and network theory
1.3 Install and configure networking services/applications1.5 Install and properly terminate various cable types and connectors using appropriate tools1.10 Identify the basic elements of unified communication technologies1.11 Compare and contrast technologies that support the cloud and virtualization1.12 Given a set of requirements, implement a basic network5.7 Given a scenario, install and configure equipment in the appropriate location using best practices
4 Ethernet Technology
2.0 Network operations5.0 Industry standards, practices, and network theory
2.6 Given a scenario, configure a switch using proper features5.4 Given a scenario, deploy the appropriate wired connectivity standard
5 IPv4 and IPv6 Addresses
1.0 Network architecture 1.8 Given a scenario, implement and configure the appropriate addressing schema
6 Routing IP Packets
1.0 Network architecture 1.9 Explain the basics of routing concepts and protocols
1.4 Explain the characteristics and benefits of various WAN technologies4.8 Given a scenario, troubleshoot and resolve common WAN issues
8 Wireless LANs
2.0 Network operations5.0 Industry standards, practices, and network theory
2.7 Install and configure wireless LAN infrastructure and implement the appropriate technologies in support of wireless capable devices4.3 Given a scenario, troubleshoot and resolve common wireless issues5.3 Given a scenario, deploy the appropriate wireless standard
9 Network Optimization
1.0 Network architecture 1.10 Identify the basic elements of unified communication technologies
10 Command-Line Tools
4.0 Troubleshooting 4.6 Given a scenario, troubleshoot and resolve common network issues
11 Network Management
2.0 Network operations5.0 Industry standards, practices, and network theory
2.1 Given a scenario, use appropriate monitoring tools2.2 Given a scenario, analyze metrics and reports from monitoring and tracking performance tools2.3 Given a scenario, use appropriate resources to support configuration management5.5 Given a scenario, implement the appropriate policies or procedures5.6 Summarize safety practices5.8 Explain the basics of change management procedures
1.2 Compare and contrast the use of networking services and applications2.4 Explain the importance of implementing network segmentation2.5 Given a scenario, install and apply patches and updates3.1 Compare and contrast risk-related concepts3.2 Compare and contrast common network vulnerabilities and threats3.3 Given a scenario, implement network hardening techniques3.4 Compare and contrast physical security controls3.5 Given a scenario, install and configure a basic firewall3.6 Explain the purpose of various network access control models3.7 Summarize basic forensic concepts4.7 Given a scenario, troubleshoot and resolve common security issues
13 Network Troubleshooting
4.0 Troubleshooting 4.1 Given a scenario, implement a network troubleshooting methodology4.2 Given a scenario, analyze and interpret the output of troubleshooting tools4.4 Given a scenario, troubleshoot and resolve common copper cable issues4.5 Given a scenario, troubleshoot and resolve common fiber cable issues
How This Book Is OrganizedAlthough this book could be read cover to cover, it is designed to be flexible and al-low you to easily move between chapters and sections of chapters to cover just the material that you need more work with. However, if you do intend to read all the chapters, the order in the book is an excellent sequence to use:
■ Chapter 1, “Computer Network Fundamentals,” introduces the purpose of computer networks and their constituent components. In addition, networks are categorized by their geography, topology, and resource location.
■ Chapter 2, “The OSI Reference Model,” presents the two network mod-els: the OSI model and the TCP/IP stack. These models categorize various network components from a network cable up to and including an application,
such as e-mail. These models are contrasted, and you are given a listing of well-known TCP and UDP port numbers used for specific applications.
■ Chapter 3, “Network Components.” A variety of network components are introduced in this chapter. You are given an explanation of various media types, the roles of specific infrastructure components, and the features provided by specialized network devices (for example, a firewall or content switch).
■ Chapter 4, “Ethernet Technology.” The most widely deployed LAN tech-nology is Ethernet, and this chapter describes the characteristics of Ethernet networks. Topics include media access, collision domains, broadcast domains, and distance/speed limitations for popular Ethernet standards. Additionally, you are introduced to some of the features available on Ethernet switches, such as VLANs, trunks, STP, link aggregation, PoE, port monitoring, and user authentication.
■ Chapter 5, “IPv4 and IPv6 Addresses.” One of the most challenging con-cepts for many CompTIA Network+ students is IP subnetting. This chapter demystifies IP subnetting by reviewing the basics of binary numbering before delving into basic subnetting and then advanced subnetting. Although most of the focus of this chapter is on IPv4 addressing, the chapter concludes with an introduction to IPv6.
■ Chapter 6, “Routing IP Packets.” A primary job of a computer network is to route traffic between subnets. This chapter reviews the operation of rout-ing IP traffic and discusses how a router obtains routing information. One way a router can populate its routing table is through the use of dynamic routing protocols, several of which are discussed in this chapter. Many environments (such as a home network connecting to the Internet via a cable modem) use NAT to convert between private IP addresses inside a network and public IP addresses outside a network. This chapter discusses Dynamic NAT (DNAT), Static NAT (SNAT), and Port Address Translation (PAT). Although the pri-mary focus on this chapter is on unicast routing, the chapter concludes with a discussion of multicast routing.
■ Chapter 7, “Wide-Area Networks.” Many corporate networks need to in-terconnect multiple sites separated by large distances. Connections between such geographically dispersed sites make up a WAN. This chapter discusses three categories of WAN connections and contrasts various WAN connection types, based on supported data rates and media types. Finally, this chapter lists characteristics for multiple WAN technologies.
■ Chapter 8, “Wireless LANs.” In this increasingly mobile world, wireless technologies are exploding in popularity. This chapter discusses the basic op-eration of WLANs. In addition, WLAN design and security considerations are addressed.
■ Chapter 9, “Network Optimization.” This chapter explains the importance of high availability for a network and what mechanisms help provide a high level of availability. Network performance optimization strategies are ad-dressed, including a section on quality of service (QoS). This chapter allows you to use what you have learned in this and preceding chapters to design a small office/home office (SOHO) network.
■ Chapter 10, “Command-Line Tools.” In your daily administration and troubleshooting of computer networks, you need familiarity with various command-line utilities available on the operating systems present in your net-work. This chapter presents a collection of popular command-line utilities for both Microsoft Windows and UNIX platforms.
■ Chapter 11, “Network Management,” reviews some of the more common tools used to physically maintain a network. The components of configuration management are also presented. This chapter discusses some of the network monitoring tools available to network administrators and what types of infor-mation are included in various logs.
■ Chapter 12, “Network Security.” Network security is an issue for most any network, and this chapter covers a variety of network security technologies. You begin by learning the goals of network security and the types of attacks you must defend against. Then you review a collection of security best prac-tices. Next, the chapter discusses specific security technologies, including fire-walls, virtual private networks (VPNs), intrusion detection systems (IDSs), and intrusion prevention systems (IPSs).
■ Chapter 13, “Network Troubleshooting.” Troubleshooting network issues is an inherent part of network administration, and this chapter presents a structured approach to troubleshooting various network technologies. Spe-cifically, you learn how to troubleshoot common Layer 2, Layer 3, and wire-less network issues.
■ Chapter 14, “Final Preparation,” reviews the exam-preparation tools avail-able in this book and the enclosed DVD. For example, the enclosed DVD contains exercises including drag and drop, matching, and simulations as well as a practice exam engine and a collection of a few training videos. Finally, a suggested study plan is presented to assist you in preparing for the CompTIA Network+ exam (N10-006).
In addition to the 13 main chapters, this book includes tools to help you verify that you are prepared to take the exam. The DVD includes drag-and-drop, matching, and simulation exercises that are an important part of your preparation for certifica-tion. The DVD also includes a practice test and memory tables that you can work through to verify your knowledge of the subject matter. Finally, the DVD contains a few videos that can assist you in mastering the content.
The popularity of wireless LANs (WLANs) has exploded over the past decade, allowing users to roam within a WLAN coverage area, take their laptops with them, and maintain network connectivity as they move throughout a building or campus environment. Many other devices, however, can take advantage of wire-less networks, such as gaming consoles, smartphones, and printers.
This chapter introduces WLAN technology, along with various wireless con-cepts, components, and standards. WLAN design considerations are then pre-sented, followed by a discussion of WLAN security.
Introducing Wireless LANs This section introduces the basic building blocks of WLANs and discusses how WLANs connect into a wired local-area network (LAN). Various design options, including antenna design, frequencies, and communications channels, are discussed, along with a comparison of today’s major wireless standards, which are all some variant of IEEE 802.11.
WLAN Concepts and Components
Wireless devices, such as laptops and smartphones, often have a built-in wireless card that allows those devices to communicate on a WLAN. But what is the device to which they communicate? It could be another laptop with a wireless card. This would be an example of an ad hoc WLAN. However, enterprise-class WLANs, and even most WLANs in homes, are configured in such a way that a wireless client connects to some sort of a wireless base station, such as a wireless access point (AP) or a wireless router. Many companies offer WiFi as a service, and when in range of an AP, it is also referred to as a hotspot , indicating that WiFi is available through the AP.
This communication might be done using a variety of antenna types, frequencies, and communication channels. The following sections consider some of these ele-ments in more detail.
Wireless Routers
Consider the basic WLAN topology shown in Figure 8-1 . Such a WLAN might be found in a residence whose Internet access is provided by digital subscriber line (DSL) modem. In this topology, a wireless router and switch are shown as separate components. However, in many residential networks, a wireless router integrates switch ports and wireless routing functionality into a single device.
Figure 8-1 Basic WLAN Topology with a Wireless Router
In Figure 8-1 , the wireless router obtains an IP address via DHCP from the Internet service provider (ISP). Then the router uses Port Address Translation (PAT), as described in Chapter 6 , “Routing IP Packets,” to provide IP addresses to devices at-taching to it wirelessly or through a wired connection. The process through which a wireless client (for example, a laptop or a smartphone) attaches with a wireless router (or wireless AP) is called association . All wireless devices associating with a sin-gle AP share a collision domain. Therefore, for scalability and performance reasons, WLANs might include multiple APs.
Wireless Access Point
Although a wireless access point (AP) interconnects a wired LAN with a WLAN, it does not interconnect two networks (for example, the service provider’s network with an internal network). Figure 8-2 shows a typical deployment of an AP.
The AP connects to the wired LAN, and the wireless devices that connect to the wired LAN via the AP are on the same subnet as the AP. (No Network Address Translation [NAT] or PAT is being performed.) This is acting as a wireless bridge between the wireless clients connected to the AP and the wired devices connected to the switch in the same Layer 2 domain.
To manage multiple APs, a company will use a Wireless LAN Controller (WLC) for centralized management and control of the APs. A Cisco model 5760 WLC would be an example of a network controller for multiple APs. The protocols used to communicate between an AP and a WLC could be the older Lightweight Ac-cess Point Protocol (LWAPP) or the more current Control And Provisioning of Wireless Access Points (CAPWAP). Using a WLC, VLAN pooling can be used to assign IP addresses to wireless clients from a pool of IP subnets and their associated VLANs.
Antennas
The coverage area of a WLAN is largely determined by the type of antenna used on a wireless AP or a wireless router. Although some lower-end, consumer-grade wire-less APs have fixed antennas, higher-end, enterprise-class wireless APs often support various antenna types.
Design goals to keep in mind when selecting an antenna include the following:
■ Required distance between an AP and a wireless client.
■ Pattern of coverage area. (For example, the coverage area might radiate out in all directions, forming a spherical coverage area around an antenna, or an an-tenna might provide increased coverage in only one or two directions.)
■ Indoor or outdoor environment.
■ Avoiding interference with other APs.
The strength of the electromagnetic waves being radiated from an antenna is re-ferred to as gain , which involves a measurement of both direction and efficiency of a transmission. For example, the gain measurement for a wireless AP’s antenna transmitting a signal is a measurement of how efficiently the power being applied to the antenna is converted into electromagnetic waves being broadcast in a specific direction. Conversely, the gain measurement for a wireless AP’s antenna receiving a signal is a measurement of how efficiently the received electromagnetic waves arriv-ing from a specific direction are converted back into electricity leaving the antenna.
Gain is commonly measured using the dBi unit of measure. In this unit of measure, the dB stands for decibels and the i stands for isotropic . A decibel, in this context, is a ratio of radiated power to a reference value. In the case of dBi, the reference value is the signal strength (power) radiated from an isotropic antenna, which represents a theoretical antenna that radiates an equal amount of power in all directions (in a spherical pattern). An isotropic antenna is considered to have gain of 0 dBi.
The most common formula used for antenna gain is the following:
GdBi = 10 * log 10 ( G )
Based on this formula, an antenna with a peak power gain of 4 ( G ) would have a gain of 6.02 dBi. Antenna theory can become mathematical (heavily relying on the use of Maxwell’s equations). However, to put this discussion in perspective, generally speaking, if one antenna has 3 dB more gain than another antenna, it has approxi-mately twice the effective power.
Antennas are classified not just by their gain but also by their coverage area. Two broad categories of antennas, which are based on coverage area, are as follows:
■ Omnidirectional: An omnidirectional antenna radiates power at relatively equal power levels in all directions (somewhat similar to the theoretical iso-tropic antenna). Omnidirectional antennas, an example of which is depicted in Figure 8-3 , are popular in residential WLANs and small office/home office (SOHO) locations.
■ Unidirectional: Unidirectional antennas can focus their power in a specific direction, thus avoiding potential interference with other wireless devices and perhaps reaching greater distances than those possible with omnidirectional antennas. One application for unidirectional antennas is interconnecting two nearby buildings, as shown in Figure 8-4 .
Another consideration for antenna installation is the horizontal or vertical orienta-tion of the antenna. For best performance, if two wireless APs communicate with one another, they should have matching antenna orientations, which is referred to as the polarity of the antenna.
Frequencies and Channels
Later in this chapter, you are introduced to a variety of wireless standards, which are all variants of the IEEE 802.11 standard. As you contrast one standard versus another, a characteristic to watch out for is the frequencies at which these standards operate. Although there are some country-specific variations, certain frequency ranges (or frequency bands ) have been reserved internationally for industrial, scien-tific, and medical purposes. These frequency bands are called the ISM bands , where ISM derives from i ndustrial, s cientific, and m edical.
Two of these bands are commonly used for WLANs. Specifically, WLANs can use the range of frequencies in the 2.4-GHz to 2.5-GHz range (commonly referred to as the 2.4-GHz band ) or in the 5.725-GHz to 5.875-GHz range (commonly referred to as the 5-GHz band ). In fact, some WLANs support a mixed environment, where 2.4-GHz devices run alongside 5-GHz devices.
Within each band are specific frequencies (or channels ) at which wireless devices op-erate. To avoid interference, nearby wireless APs should use frequencies that do not overlap with one another. Using wireless survey tools such as AirMagnet from Fluke Networks can provide analysis of what is currently in use, allowing you to set up a new wireless system that does not compete for the same frequencies that are already in use. Those same tools can assist in identifying wireless channel utilization as well in existing and new wireless networks. Regarding channel selection, merely selecting different channels is not sufficient, however, because transmissions on one channel spill over into nearby channels. Site survey tools can collect data to show the relative strength of signals in the areas being serviced by the APs. This output can be color-coded and overlaid on top of the floor plan and is often referred to as a heat map of the wireless signals.
Consider, for example, the 2.4-GHz band. Here, channel frequencies are separated by 5 MHz (with the exception of channel 14, which has 12 MHz of separation from channel 13). However, a single channel’s transmission can spread over a frequency range of 22 MHz. As a result, channels must have five channels of separation (5 * 5 MHz = 25 MHz, which is greater than 22 MHz). You can see from Figure 8-5 that, in the United States, you could select nonoverlapping channels of 1, 6, and 11.
The 5-GHz band has a higher number of channels, as compared to the 2.4-GHz band. Table 8-2 lists the recommended nonoverlapping channels for the 5-GHz band in the United States. Note that additional channels are supported in some countries.
Table 8-2 Nonoverlapping Channels in the 5-GHz Band Recommended for Use in the United
States
Channel Frequency (GHz)
36 5.180
40 5.200
44 5.220
48 5.240
52 5.260*
56 5.280*
60 5.300*
64 5.320*
100 5.500**
104 5.520**
108 5.540**
112 5.560**
116 5.580**
136 5.680**
140 5.700**
149 5.745
153 5.765
157 5.785
161 5.805
165 5.825
*Must support dynamic frequency selection to prevent interference with RADAR **Must be professionally installed
CSMA/CA
In Chapter 4 , “Ethernet Technology,” you learned about Ethernet’s carrier sense multiple access collision detection (CSMA/CD) technology. WLANs use a similar technology called carrier sense multiple access collision avoidance (CSMA/CA). Just
as CSMA/CD is needed for half-duplex Ethernet connections, CSMA/CA is needed for WLAN connections because of their half-duplex operation. Similar to the way an Ethernet device listens to an Ethernet segment to determine whether a frame ex-ists on the segment, a WLAN device listens for a transmission on a wireless channel to determine whether it is safe to transmit. In addition, the collision-avoidance part of the CSMA/CA algorithm causes wireless devices to wait for a random backoff time before transmitting.
Transmission Methods
In the previous discussion, you saw the frequencies used for various wireless chan-nels. However, be aware that those frequencies are considered to be the center fre-
quencies of a channel. In actual operation, a channel uses more than one frequency, which is a transmission method called spread spectrum . These frequencies are, how-ever, very close to one another, which results in a narrowband transmission .
The three variations of spread-spectrum technology to be aware of for your study of WLANs include the following:
■ Direct-sequence spread spectrum (DSSS): Modulates data over an entire range of frequencies using a series of symbols called chips . A chip is shorter in duration than a bit, meaning that chips are transmitted at a higher rate than the actual data. These chips encode not only the data to be transmitted, but also what appears to be random data. Although both parties involved in a DSSS communication know which chips represent actual data and which chips do not, if a third party intercepted a DSSS transmission, it would be difficult for him to eavesdrop on the data because he would not easily know which chips repre-sented valid bits. DSSS is more subject to environmental factors, as opposed to FHSS and OFDM, because of its use of an entire frequency spectrum.
■ Frequency-hopping spread spectrum (FHSS): Allows the participants in a communication to hop between predetermined frequencies. Security is en-hanced because the participants can predict the next frequency to be used, but a third party cannot easily predict the next frequency. FHSS can also provision extra bandwidth by simultaneously using more than one frequency.
■ Orthogonal frequency-division multiplexing (OFDM): Whereas DSSS uses a high modulation rate for the symbols it sends, OFDM uses a relatively slow modulation rate for symbols. This slower modulation rate, combined with the simultaneous transmission of data over 52 data streams, helps OFDM support high data rates while resisting interference between the various data streams.
Of these three wireless modulation techniques, only DSSS and OFDM are com-monly used in today’s WLANs.
Most modern WLAN standards are variations of the original IEEE 802.11 stan-dard, which was developed in 1997. This original standard supported a DSSS and an FHSS implementation, both of which operated in the 2.4-GHz band. However, with supported speeds of 1 Mbps or 2 Mbps, the original 802.11 standard lacks suf-ficient bandwidth to meet the needs of today’s WLANs. The most popular variants of the 802.11 standard in use today are 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac, as described in detail in the following sections.
802.11a
The 802.11a WLAN standard, which was ratified in 1999, supports speeds as high as 54 Mbps. Other supported data rates (which can be used if conditions are not suitable for the 54 Mbps rate) include 6, 9, 12, 18, 24, 36, and 48 Mbps. The 802.11a standard uses the 5-GHz band and uses the OFDM transmission method. Interestingly, 802.11a never gained widespread adoption because it was not back-ward compatible with 802.11b, whereas 802.11g was backward compatible.
802.11b
The 802.11b WLAN standard, which was ratified in 1999, supports speeds as high as 11 Mbps. However, 5.5 Mbps is another supported data rate. The 802.11b stan-dard uses the 2.4-GHz band and uses the DSSS transmission method.
802.11g
The 802.11g WLAN standard, which was ratified in 2003, supports speeds as high as 54 Mbps. Like 802.11a, other supported data rates include 6, 9, 12, 18, 24, 36, and 48 Mbps. However, like 802.11b, 802.11g operates in the 2.4-GHz band, which allows it to offer backward compatibility to 802.11b devices. 802.11g can use either the OFDM or the DSSS transmission method.
802.11n
The 802.11n WLAN standard, which was ratified in 2009, supports a wide variety of speeds, depending on its implementation. Although the speed of an 802.11n network could exceed 300 Mbps (through the use of channel bonding , as discussed later), many 802.11n devices on the market have speed ratings in the 130–150 Mbps range. Inter-estingly, an 802.11n WLAN could operate in the 2.4-GHz band, the 5-GHz band, or both simultaneously. 802.11n uses the OFDM transmission method.
One way 802.11n achieves superior throughput is through the use of a technol-ogy called multiple input, multiple output (MIMO). MIMO uses multiple antennas for transmission and reception. These antennas do not interfere with one another, thanks to MIMO’s use of spatial multiplexing , which encodes data based on the an-tenna from which the data will be transmitted. Both reliability and throughput can be increased with MIMO’s simultaneous use of multiple antennas.
Yet another technology implemented by 802.11n is channel bonding . With channel bonding, two wireless bands can be logically bonded together, forming a band with twice the bandwidth of an individual band. Some literature refers to channel bond-ing as 40-MHz mode , which is the bonding of two adjacent 20-MHz bands into a 40-MHz band.
The 802.11n high throughput (HT) standard defines modes for ensuring that older a/b/g devices and newer 802.11n devices can avoid collisions with each other.
802.11ac
The 802.11ac WLAN standard was published in 2013 and builds on (and is faster and more scalable than) 802.11n. 802.11ac is a 5-GHz only technology that can use wider channels in the 5-GHz band, more spatial streams, and multi-user MIMO (MU-MIMO).
802.11x Standard Summary
Table 8-3 acts as a reference to help you contrast the characteristics of the 802.11 standards.
Table 8-3 Characteristics of 802.11 Standards
Standard Band Max. Bandwidth Transmission Method Max. Range
802.11 2.4 GHz 1 Mbps or 2 Mbps DSSS or FHSS 20 m indoors /100 m outdoors
802.11a 5 GHz 54 Mbps OFDM 35 m indoors/120 m outdoors
802.11b 2.4 GHz 11 Mbps DSSS 32 m indoors/140 m outdoors
802.11g 2.4 GHz 54 Mbps OFDM or DSSS 32 m indoors/140 m outdoors
802.11n 2.4 GHz or 5 GHz (or both)
> 300 Mbps (with channel bonding)
OFDM 70 m indoors/250 m outdoors
802.11ac 5 GHz > 3 Gbps (with MU-MIMO and several antennas)
Deploying Wireless LANs When designing and deploying WLANs, you have a variety of installation options and design considerations. This section delves into your available options and pro-vides you with some best practice recommendations.
Types of WLANs
WLANs can be categorized based on their use of wireless APs. The three main categories are independent basic service set (IBSS), basic service set (BSS), and ex-tended service set (ESS). An IBSS WLAN operates in an ad hoc fashion, while BSS and ESS WLANs operate in infrastructure mode. The following sections describe the three types of WLANs in detail.
IBSS
As shown in Figure 8-6 , a WLAN can be created without the use of an AP. Such a configuration, called an IBSS, is said to work in an ad hoc fashion. An ad hoc WLAN is useful for temporary connections between wireless devices. For example, you might temporarily interconnect two laptop computers to transfer a few files.
InternetServiceProvider
Switch Router
Laptop Laptop
Figure 8-6 Independent Basic Service Set (IBSS) WLAN
Figure 8-7 depicts a WLAN using a single AP. WLANs that have just one AP are called BSS WLANs. BSS WLANs are said to run in infrastructure mode because wireless clients connect to an AP, which is typically connected to a wired network infrastructure. A BSS network is often used in residential and SOHO locations, where the signal strength provided by a single AP is sufficient to service all the WLAN’s wireless clients.
InternetServiceProvider
Switch Router
Laptop
WirelessAccessPoint
Laptop
Figure 8-7 Basic Service Set (BSS) WLAN
ESS
Figure 8-8 illustrates a WLAN using two APs. WLANs containing more than one AP are called ESS WLANs . Like BSS WLANs, ESS WLANs operate in infrastruc-ture mode. When you have more than one AP, take care to prevent one AP from interfering with another. Specifically, the previously discussed nonoverlapping chan-nels (channels 1, 6, and 11 for the 2.4-GHz band) should be selected for adjacent wireless coverage areas.
A mesh wireless network is a collection of wireless devices that may not use central-ized control (decentralized management). The combined wireless coverage range defines the range of the network. This could also be referred to as a mesh cloud . Ad-ditional wireless technologies (besides WiFi) could be used to build a mesh wireless topology. This type of network could be used for hosts to communicate with other devices in the mesh, or the network could provide a gateway to the Internet or other networks.
Sources of Interference
A major issue for WLANs is radio frequency interference (RFI) caused by other devices using similar frequencies to the WLAN devices. Also, physical obstacles can impede or reflect WLAN transmissions. The following are some of the most com-mon sources of interference:
■ Other WLAN devices: Earlier in this chapter, you read about nonoverlap-ping channels for both the 2.4-GHz and 5-GHz bands. However, if two or more WLAN devices are in close proximity and use overlapping channels, those devices could interfere with one another.
■ Cordless phones: Several models of cordless phones operate in the 2.4-GHz band and can interfere with WLAN devices. However, if you need cordless phones to coexist in an environment with WLAN devices using the 2.4-GHz band, consider the use of digital enhanced cordless telecommunications (DECT) cordless phones. Although the exact frequencies used by DECT cordless phones vary based on country, DECT cordless phones do not use the 2.4-GHz band. For example, in the United States, DECT cordless phones use frequencies in the range 1.92 GHz to 1.93 GHz.
■ Microwave ovens: Older microwave ovens, which might not have sufficient shielding, can emit relatively high-powered signals in the 2.4-GHz band, resulting in significant interference with WLAN devices operating in the 2.4-GHz band.
■ Wireless security system devices: Most wireless security cameras operate in the 2.4-GHz frequency range, which can cause potential issues with WLAN devices.
■ Physical obstacles: In electromagnetic theory, radio waves cannot propagate through a perfect conductor. So, although metal filing cabinets and large ap-pliances are not perfect conductors, they are sufficient to cause degradation of a WLAN signal. For example, a WLAN signal might hit a large air condi-tioning unit, causing the radio waves to be reflected and scattered in multiple directions. Not only does this limit the range of the WLAN signal, but radio waves carrying data might travel over different paths. This multipath issue can cause data corruption. Concrete walls, metal studs, or even window film could reduce the quality of the wireless network signals.
■ Signal strength: The range of a WLAN device is a function of the device’s sig-nal strength. Lower-cost consumer-grade APs do not typically allow an adminis-trative adjustment of signal strength. However, enterprise-class APs often allow signal strength to be adjusted to ensure sufficient coverage of a specific area, while avoiding interference with other APs using the same channel.
As you can see from this list, most RFI occurs in the 2.4-GHz band as opposed to the 5-GHz band. Therefore, depending on the wireless clients you need to sup-port, you might consider using the 5-GHz band, which is an option for 802.11a and 802.11n WLANs. With the increased use of wireless, both coverage and capacity-based planning should be done to provide acceptable goodput. Goodput refers to the number of useful information bits that the network can deliver (not including overhead for the protocols being used). Another factor is the density (ratio of users to APs), which if too high could harm performance of the network. Areas expecting high density would include classrooms, hotels, and hospitals. Device or bandwidth saturation could impact performance.
WLANs using more than one AP (an ESS WLAN) require careful planning to prevent the APs from interfering with one another, while still servicing a desired coverage area. Specifically, an overlap of coverage between APs should exist to allow uninterrupted roaming from one WLAN cell (which is the coverage area provided by an AP) to another. However, those overlapping coverage areas should not use overlapping frequencies.
Figure 8-9 shows how nonoverlapping channels in the 2.4-GHz band can overlap their coverage areas to provide seamless roaming between AP coverage areas. A common WLAN design recommendation is to have a 10–15 percent overlap of cov-erage between adjoining cells.
Channel 6Channel 1
Channel 11
Figure 8-9 10 Percent to 15 Percent Coverage Overlap in Coverage Areas for Nonoverlapping
Channels
If a WLAN has more than three APs, the APs can be deployed in a honeycomb fashion to allow an overlap of AP coverage areas while avoiding an overlap of iden-tical channels. The example shown in Figure 8-10 shows an approach to channel selection for adjoining cells in the 2.4-GHz band. Notice that cells using the same nonoverlapping channels (channels 1, 6, and 11) are separated by another cell. For example, notice that none of the cells using channel 11 overlap another cell using channel 11.
Figure 8-10 Nonoverlapping Coverage Cells for the 2.4-GHz Band
NOTE Although a honeycomb channel assignment scheme can be used for the 5-GHz band, identical channels should be separated by at least two cells, rather than the single cell shown for the 2.4-GHz band.
Securing Wireless LANs WLANs introduce some unique concerns to your network. For example, improp-erly installed wireless APs are roughly equivalent to putting an Ethernet port in a building’s parking lot, where someone can drive up and access your network. For-tunately, various features are available to harden the security of your WLAN, as discussed in this section.
Security Issues
In the days when dial-up modems were popular, malicious users could run a pro-gram on their computer to call all phone numbers in a certain number range. Phone numbers that answered with modem tone became targets for later attacks. This type of reconnaissance was known as war dialing . A modern-day variant of war dialing is war driving , where potentially malicious users drive around looking for unsecured WLANs. These users might be identifying unsecured WLANs for nefarious pur-poses or simply looking for free Internet access. Devices like cell phones, laptops, tablets, and gaming and media devices could act as wireless clients as well as be used in a wireless attack as they have potential WiFi access to the network.
Other WLAN security threats include the following:
■ War chalking: Once an open WLAN (or a WLAN whose SSID and authen-tication credentials are known) is found in a public place, a user might write a symbol on a wall (or some other nearby structure) to let others know the char-acteristics of the discovered network. This practice, which is a variant of the decades-old practice of hobos leaving symbols as messages to fellow hobos, is called war chalking . Figure 8-11 shows common war-chalking symbols.
Open node
Closed node
ssid
ssid
WEP node
ssid accesscontact
bandwidth
bandwidth
W
Figure 8-11 War-Chalking Symbols
■ WEP and WPA security cracking: As discussed later in this chapter, various security standards are available for encrypting and authenticating a WLAN client with an AP. Two of the less secure standards include Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). Although WPA is consid-ered more secure than WEP, utilities are available on the Internet for cracking each of these approaches to wireless security. By collecting enough packets transmitted by a secure AP, these cracking utilities can use mathematical al-gorithms to determine the preshared key (PSK) configured on a wireless AP, with which an associating wireless client must also be configured.
■ Rogue access point: A malicious user could set up his own AP to which le-gitimate users would connect. Such an AP is called a rogue access point . That malicious user could then use a packet sniffer (which displays information about unencrypted traffic, including the traffic’s data and header information) to eavesdrop on communications flowing through his AP. To cause unsuspect-ing users to connect to the rogue AP, the malicious user could configure the rogue AP with the same service set identifier (SSID) as used by a legitimate AP. When a rogue AP is configured with the SSID of a legitimate AP, the rogue AP is commonly referred to as an evil twin.
NOTE An SSID is a string of characters identifying a WLAN. APs participating in the same WLAN (in an ESS) can be configured with identical SSIDs. An SSID shared among multiple APs is called an extended service set identifier (ESSID).
Approaches to WLAN Security
A WLAN that does not require authentication or provide encryption for wireless devices (for example, a publicly available WLAN found in many airports) is said to be using open authentication . To protect WLAN traffic from eavesdroppers, a variety of security standards and practices have been developed, including the following:
■ MAC address filtering: An AP can be configured with a listing of MAC ad-dresses that are permitted to associate with the AP. If a malicious user attempts to connect via his laptop (whose MAC address is not on the list of trusted MAC addresses), that user is denied access. One drawback to MAC address filtering is the administrative overhead required to keep an approved list of MAC addresses up-to-date. Another issue with MAC address filtering is that a knowledgeable user could falsify the MAC address of his wireless network card, making his device appear to be approved.
■ Disabling SSID broadcast: An SSID can be broadcast by an AP to let users know the name of the WLAN. For security purposes, an AP might be con-figured not to broadcast its SSID. However, knowledgeable users could still determine the SSID of an AP by examining captured packets.
■ Preshared key: To encrypt transmission between a wireless client and an AP (in addition to authenticating a wireless client with an AP), both the wireless client and the AP could be preconfigured with a matching string of characters (a PSK, as previously described). The PSK could be used as part of a math-ematical algorithm to encrypt traffic, such that if an eavesdropper intercepted the encrypted traffic, he would not be able to decrypt the traffic without knowing the PSK. Although using a PSK can be effective in providing security for a small network (for example, a SOHO network), it lacks scalability. For example, in a large corporate environment, a PSK being compromised would necessitate the reconfiguration of all devices configured with that PSK.
NOTE WLAN security based on a PSK technology is called personal mode .
■ IEEE 802.1X: Rather than having all devices in a WLAN be configured with the same PSK, a more scalable approach is to require all wireless users to au-thenticate using their own credentials (for example, a username and password). Allowing each user to have his own set of credentials prevents the compromis-ing of one password from impacting the configuration of all wireless devices. IEEE 802.1x is a technology that allows wireless clients to authenticate with an authentication server (typically, a Remote Authentication Dial-In User Ser-vice [RADIUS] server).
NOTE WLAN security based on IEEE 802.1x and a centralized authentication server such as RADIUS is called enterprise mode .
Chapter 4 discussed IEEE 802.1X in detail and described the role of a supplicant, an authenticator, and an authentication server, but Chapter 4 showed how IEEE 802.1X was used in a wired network. Figure 8-12 shows a wireless implementation of IEEE 8021X.
NOTE IEEE 802.1S works in conjunction with an Extensible Authentication Proto-col (EAP) to perform its job of authentication. A variety of EAP types exist, including Lightweight Extensible Authentication Protocol (LEAP), EAP-Flexible Authentica-tion via Secure Tunneling (EAP-FAST), EAP-Transport Layer Security (EAP-TLS), EAP-Tunneled Transport Layer Security (EAP-TTLS), Protected EAP–Generic Token Card (PEAP-GTC), and Protected EAP–Microsoft Challenge Handshake Authentication Protocol version 2 (PEAP-MSCHAPv2). Although these EAP types differ in their procedures, the overriding goal for each EAP type is to securely au-thenticate a supplicant and provide the supplicant and the authenticator a session key that can be used during a single session in the calculation of security algorithms (for example, encryption algorithms).
Security Standards
When configuring a wireless client for security, the most common security stan-dards from which you can select are as follows:
■ Wired Equivalent Privacy (WEP)
■ Wi-Fi Protected Access (WPA)
■ Wi-Fi Protected Access Version 2 (WPA2)
The following sections describe these standards in detail.
WEP
The original 802.11 standard did address security; however, the security was a WEP key. With WEP, an AP is configured with a static WEP key. Wireless clients need-ing to associate with an AP are configured with an identical key (making this a PSK approach to security). The 802.11 standard specifies a 40-bit WEP key, which is considered to be a relatively weak security measure.
Because a WEP key is a static string of characters, it could be compromised with a brute-force attack, where an attacker attempts all possible character combinations until a match for the WEP key is found. Another concern, however, is that WEP uses RC4 as its encryption algorithm.
NOTE RC4 (which stands for Ron’s Code or Rivest Cipher because it was developed by Ron Rivest of RSA Security) is sometimes pronounced arc 4 .
RC4 uses a 24-bit initialization vector (IV), which is a string of characters added to the transmitted data, such that the same plain-text data frame will never appear as the same WEP-encrypted data frame. However, the IV is transmitted in clear text. So, if a malicious user, using packet-capture software, captures enough packets hav-ing the same WEP key, and because the malicious user can see the IV in clear text, he can use a mathematical algorithm (which can be performed with WEP-cracking software found on the Internet) to determine the static WEP key.
Some WEP implementations support the use of a longer WEP key (for example, 128 bits instead of 40 bits), making a WEP key more difficult to crack; however, both the wireless clients and their AP must support the longer WEP key.
WPA
The Wi-Fi Alliance (a nonprofit organization formed to certify interoperability of wireless devices) developed its own security standard, WPA, to address the weak-nesses of WEP. Some of the security enhancements offered by WPA include the following:
■ WPA operating in enterprise mode can require a user to be authenticated be-fore keys are exchanged.
■ In enterprise mode, the keys used between a wireless client and an access point are temporary session keys.
■ WPA uses Temporal Key Integrity Protocol (TKIP) for enhanced encryp-tion. Although TKIP does rely on an initialization vector, the IV is expanded from WEP’s 24-bit IV to a 48-bit IV. Also, broadcast key rotation can be used, which causes a key to change so quickly that an eavesdropper would not have time to exploit a derived key.
■ TKIP leverages Message Integrity Check (MIC), which is sometimes referred to as Message Integrity Code (MIC). MIC can confirm that data was not modi-fied in transit.
Although not typically written as WPA1, when you see the term WPA , consider it to be WPA Version 1 (WPA1). WPA Version 2, however, is written as WPA2 .
WPA2
In 2004, the IEEE 802.11i standard was approved and required stronger algorithms for encryption and integrity checking than those seen in previous WLAN security protocols such as WEP and WPA. The requirements set forth in the IEEE 802.11i standard are implemented in the Wi-Fi Alliance’s WPA Version 2 (WPA2) security
standard. WPA2 uses Counter Mode with Cipher Block Chaining Message Authen-tication Code Protocol (CCMP) for integrity checking and Advanced Encryption Standard (AES) for encryption. WPA2 that uses a centralized server for authenticating users is referred to as Enterprise mode. An implementation of WPA2 that uses a con-figured password or PSK instead of a centralized server is referred to as Personal mode.
Additional Wireless Options
Other wireless technologies, such as Bluetooth, infrared (IR), and near-field com-munications (NFC), which are often integrated into smartphones, can also provide connectivity for a personal-area network (PAN) or other short-range networking applications.
Real-World Case Study Acme Inc. hired an outside contractor who specializes in WiFi. The consultants came in and did a needs assessment and performed a wireless site survey. Recom-mendations were then made about the need for 15 access points in the headquarters office spaces and three access points at each of the remote branch offices. Three wireless LAN controllers, one for each office, will be used to manage the respective access points. The management of the access points through the wireless LAN con-trollers will be done primarily through the headquarters office using the WAN that is connecting the branch offices to the headquarters office.
Because of the high number of other WiFi access points being used in the same building as the headquarters office, Acme Inc. decided to use the 5-GHz range (due to less competition in that space) and to use 802.11n.
For security, Acme will use WPA2 in conjunction with a RADIUS server. ACME will use Enterprise mode for authentication of each user before allowing them access on the wireless network(s). The RADIUS server is integrated with Microsoft Active Directory so that Acme will not have to re-create every user account; the RADIUS server can check with the Active Directory server to verify user credentials and pass-words.
There are separate SSIDs set up that map to the various VLANs and departments that are currently on the wired network. There is also a separate SSID set up as a wireless guest network that has limited access but does provide Internet access for guest users.
Once in place, a site survey was done again to verify the signal strengths and to iden-tify any interference related to the wireless implementation. A heat map was pro-vided to visually represent the signal strengths in the coverage areas in the respective office space.
Summary The main topics covered in this chapter are the following:
■ Various components, technologies, and terms used in WLANs were identified.
■ WLAN design considerations were presented, such as the selection of WLAN standards, bands, and nonoverlapping channels. Potential sources of interfer-ence were also identified.
■ Some of the security risks posed by a WLAN were described and the tech-nologies available for mitigating those risks were presented.
Exam Preparation Tasks
Review All the Key Topics Review the most important topics from inside the chapter, noted with the Key Topic icon in the outer margin of the page. Table 8-4 lists these key topics and the page numbers where each is found.
Table 8-4 Key Topics for Chapter 8
Key Topic Element Description Page Number
Figure 8-1 Basic WLAN topology with a wireless router 269
Figure 8-2 Basic WLAN topology with a wireless access point 270
List Antenna selection criteria 271
Figure 8-3 Omnidirectional antenna coverage 272
Figure 8-4 Unidirectional antenna coverage 272
Figure 8-5 Nonoverlapping channels in the 2.4-GHz band 274
List Spread spectrum transmission methods 276
Table 8-3 Characteristics of 802.11 standards 278
Figure 8-6 Independent basic service set (IBSS) WLAN 279
Figure 8-7 Basic service set (BSS) WLAN 280
Figure 8-8 Extended service set (ESS) WLAN 281
List Sources of interference 281
Figure 8-9 10 percent to 15 percent coverage overlap in coverage areas for nonoverlapping channels
Figure 8-10 Nonoverlapping coverage cells for the 2.4-GHz band 284
List Wireless security threats 285
List Security standards and best practices 286
Figure 8-12 IEEE 802.1X security for a WLAN 287
Complete Tables and Lists from Memory Print a copy of Appendix D , “Memory Tables” (found on the DVD), or at least the section for this chapter, and complete the tables and lists from memory. Appendix E , “Memory Table Answer Key,” also on the DVD, includes the completed tables and lists so you can check your work.
Define Key Terms Define the following key terms from this chapter, and check your answers in the Glossary:
wireless access point (AP), wireless router, decibel (dB), omnidirectional an-tenna, unidirectional antenna, carrier sense multiple access collision avoidance (CSMA/CA), direct-sequence spread spectrum (DSSS), frequency-hopping spread spectrum (FHSS), orthogonal frequency-division multiplexing (OFDM), 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac multiple input, multiple output (MIMO), channel bonding, independent basic service set (IBSS), basic service set (BSS), extended service set (ESS), war chalking, service set identifier (SSID), Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA), Wi-Fi Pro-tected Access Version 2 (WPA2), Enterprise mode, Personal mode
Complete Chapter 8 Hands-On Labs in Network+ Simulator ■ Matching Wireless Standards and Terminology
■ Wireless Security Terminology
■ Wireless Antenna Placement
■ Manually Configuring Wireless Signals on a Small Office/Home Office Router
Review Questions
The answers to these review questions are in Appendix A , “Answers to Review Questions.”
1. What type of antenna, commonly used in wireless APs and wireless routers in SOHO locations, radiates relatively equal power in all directions?
a. Unidirectional
b. Yagi
c. Parabolic
d. Omnidirectional
2. When using the 2.4-GHz band for multiple access points in a WLAN lo-cated in the United States, which nonoverlapping channels should you select? (Choose three.)
7. When extending the range for a 2.4-GHz WLAN, you can use nonoverlap-ping channels for adjacent coverage cells. However, there should be some overlap in coverage between those cells (using nonoverlapping channels) to prevent a connection from dropping as a user roams from one coverage cell to another. What percentage of coverage overlap is recommended for these adja-cent cells?
a. 5 percent to 10 percent
b. 10 percent to 15 percent
c. 15 percent to 20 percent
d. 20 percent to 25 percent
8. If a WLAN does not require a user to provide credentials to associate with a wireless AP and access the WLAN, what type of authentication is said to be in use?
a. WEP
b. SSID
c. Open
d. IV
9. WEP’s RC4 approach to encryption uses a 24-bit string of characters added to transmitted data, such that the same plain-text data frame will never appear as the same WEP-encrypted data frame. What is this string of characters called?
a. Initialization vector
b. Chips
c. Orthogonal descriptor
d. Session key
10. What standard developed by the Wi-Fi Alliance implements the requirements of IEEE 802.11i?
notification), 256 believability of a route, 208 benefits
of bus topologies, 12 of client/server networks, 20 of full-mesh topologies, 17 of hub-and-spoke topologies, 16 of partial-mesh topologies, 19 of peer-to-peer networks, 22 of ring topologies, 13 of star topologies, 15
best practices for high availability, 302 best-effort QoS, 306 BGP (Border Gateway Protocol),
536 CHAP (Challenge-Handshake Authentication Protocol)
CHAP (Challenge-Handshake Authentication Protocol), 241
characteristics of bus topologies, 12 of client/server networks, 20 of full-mesh topologies, 17 of hub-and-spoke topologies, 16 of LLC sublayer, 38 - 40 of MAC sublayer, 37 - 38 of network infrastructure devices, 89 of partial-mesh topologies, 19 of peer-to-peer networks, 22 of ring topologies, 13 of routing protocols, 207 - 212
administrative distance, 208
metrics, 208
of star topologies, 15 cheapernet, 114 CIDR (classless interdomain routing),
of bus topologies, 12 of client/server networks, 20 of full-mesh topologies, 17 of hub-and-spoke topologies, 16 of partial-mesh topologies, 19 of peer-to-peer networks, 22 of ring topologies, 13 of star topologies, 15
distance limitations of Ethernet, 120 - 122
distance-vector routing protocols, 210 - 212
DMZ (demilitarized zone), 430 DNAT (Dynamic NAT), 216 DNS (Domain Name System), 53